This invention relates to a compound semiconductor vapor phase epitaxial device for improving uniformity in composition and reproducibility of a compound semiconductor crystal formed on a crystal substrate.
A metalorganic chemical vapor deposition, method is well known, which is a typical example of compound semiconductor vapor phase film formation methods capable of controlling thickness and composition of the film and, which is excellent in productivity, and thus, is widely utilized for the crystal growth of GaAs, which is, a typical compound semiconductor of the groups III-V elements.
In the MOCVD of the groups III-V elements compound semiconductor, the crystal growth is generally performed under an atmosphere in which the group V elements material is excessively supplied, and in such case, the crystal growth rate is in proportion to the supply amount of the group III elements material.
Further, nitride semiconductors such as GaN or AlGaN in the group III-V semiconductors are being studied as short wavelength light emitting elements, and experimental examples of the MOCVD utilizing, as materials, NH.sub.3, TMG (trimethylgallium) or TMA(trimethylaluminium) have been announced.
In a system, however, in which such materials are utilized, the NH.sub.3 and the TMG, and the NH.sub.3 and the TMA react respectively at room temperature (particularly, the NH.sub.3 and the TMA are remarkably reacted), and accordingly, when the materials are supplied, these material are preliminarily mixed and the mixture is then guided into a reactor or reaction device. In such method, there are problems such that the composition of the film formed on the crystal substrate is not uniform and good reproducibility is not obtained. These problems are remarkably observed in the case of AlGaN mixed crystal.
In order to eliminate such problems, as disclosed in Japanese Patent Laid-open Publication No. 61-202422, the material gases are independently supplied to reaction areas, i.e. growth areas on the crystal substrate. However, it is difficult to uniformly grow the crystal on the crystal substrate only by independently supplying the material gases and mixing them in the reaction areas because of generation of vortices and turbulent flow in the gas flow. Furthermore, there is disclosed in Japanese Patent Laid-open Publication No. 61-186288 an angular reaction tube in consideration of the flow of the material gases. However, the above-mentioned problems cannot be solved by this angular reaction tube.